Mark

On 767's, there are two UFI (Universal Fault Interrupter) units that protect the center tank pumps and wiring.

We recently had a right pump that was only receiving one (out of three) 115VAC inputs. A control relay upstream of the pump had only one phase also.

Traveling further upstream is the UFI. There were some fault lights on the unit indicating a phase problem.

So, you get a replacement and hang it off the plug (thinking it'll work). No lights..... no nothing?

Hang it off the known good side..... same thing?

The only possible issue would be case grounding, which it turned out to be. Most all aircraft electrical components have a wired ground. Not the UFI's.

Not really a big deal, but it sure makes you think for a second.